EF1 tornado in Lassen County, California

A mesoanticyclone embedded within a deep pyrocumulonimbus updraft inside the Loyalton wildfire perimeter generated an EF1 rated anticyclonic tornado that snapped several quaking aspen trees (DI 27, DOD 4) along a 0.09-mile path on the northeast facing slope of Roberts Canyon. The tornado spun up 0.37 miles south-southwest of the intersection of Forest Service Road 182 and Forest Service Road 31182 and dissipated 0.46 miles south-southwest of the aforementioned intersection. The damage path had a maximum width of 20 yards. No injuries or deaths occurred with this tornado.

Dry conditions and anomalously low fuel moisture, in combination with an unstable low-to-mid-level atmosphere, allowed the Loyalton wildfire to develop extreme fire behavior on the afternoon of 15 August 2020. Robust heat and moisture fluxes from the wildfire caused rapid smoke plume deepening and lofting of pyrometeors above the lifting condensation level, which led to the formation of two vertically extensive pyrocumulonimbi and three tornadoes.